Fan control system



y 3 1956 N. w. STUNKARD FAN CONTROL SYSTEM Filed Sept. 29, 1952//\/L//\/7-UR Norman W Jfunkara FAN CONTROL SYSTEM Norman W. Stunkard,Portland, Oreg., assignor to Iron Fireman Manufacturing Company,Portland, Greg.

Application September 29, 1952, Serial No. 312,144

4 Claims. (Cl. 236-49) This invention relates generally to air flowsystems and more particularly to an air flow system which is required tosupply air for a needed use at two different rates of fiow in responseto the attainment of two different values of a condition of the systems.

To illustrate a use of one form of my system this disclosure is directedto a forced warm air heating system for a residence. It is assumed thatin this system there is a warm air furnace heated by an automatic fuelburner which operates to heat the furnace when a thermostat in theliving space of the house indicates that heat is required. It is furtherassumed that a Warm air duct system is provided to conduct cool air fromthe living space to the interior of a casing surrounding the warm airfurnace and back to the living space and that in the duct system is amotor driven fan adapted to impel the air through the duct system.

It should be understood that in such a heating system it is desirable tokeep the air circulating through the duct system at all times to preventstratification of the air but that if the air is not warmed to a comforttemperature the air circulating fan should be stopped to prevent thefeeling of cold drafts. It should further be understood that it has beenfound highly desirable to cause the fan to circulate air through theduct system at a lower rate when the air temperature at the furnace isbelow a preset temperature and to cause the fan to circulate air at ahigher rate when the air temperature at the furnace is above said presettemperature. In the past various schemes have been used to change therate of air flow through the duct system but the most common way hasbeen to provide a two speed motor for the fan.

I have found that where a fan, having a housing of generally logarithmicspiral shape and having a fan wheel of either the paddle wheel ormultiblade type, has a usual high capacity direction of rotation, itwill also deliver air but at a greatly reduced rate when rotated in theopposite direction at normal speed. Also by experiment 1 have found thatI can greatly vary the discharge of the fan when rotated in the reversedirection by varying the blade design of the fan. Practically I havefound that it is a relatively simple matter of varying the angle of thefan blades at their outlet ends or tips with respect to a radial linethrough each blade tip to give the desired relation of fan discharge atreverse rotation to fan discharge at forward rotation. In practice Ilike to hold this relation at about one third for the duty described.

In the air flow control system of this invention I have discovered thata reversible fan of the above type driven by a reversible motor of thetype shown in U. S. Patent 2,382,827 issued August 14, 1945, to ChesterE. Sprague is convenient to use and economical to apply. However for mypurpose I usually replace the separate controller shown in the Spraguepatent with a magnetic switch secured to the motor frame and a twovalued condition responsive switch remotely mounted at the bonnet of thefurnace. In this case the condition responsive switch '"nited StatesPatent comprises a single temperature responsive actuator adapted tooperate two single pole, single throw, nor mally open, switches one ofthe switches being set to close at a lower temperature of, say, F. andthe other being set to close at a higher temperature of, say, 140 F.

It will be seen that in the above arrangement I have provided means forcontrolling the air flow means of a forced warm air furnace installationso that when the furnace bonnet temperature is below, say, F. a minimumof air will flow through the system, but when the air temperature at thefurnace bonnet reaches 110 F. the lower setting bonnet switch closes tostart the motor and fan in the reverse direction thus circulating air ata rate of about one-third of the full fan capacity. Then if the furnacetemperature at the bonnet increases to F., say, the higher settingbonnet switch closes, thus reversing the motor to cause it to rotate inthe normal or high capacity direction of fan rotation. These sequentialcontrol changes are reversed when sufiicient heat has been supplied tothe living space of the residence so that the room thermostat stops theburner and the furnace temperature gradually is reduced.

It is a principal object of this invention to provide a simple, safe,and economical means for limiting the flow of air in a warm air heatingsystem to a small amount when the air at the heat supply is below afirst preset temperature, to increase the flow of air through the systemto a first preset rate when the air at the heat supply is above saidfirst preset temperature and below a second, but higher, presettemperature, and to increase the flow of air through the system to asecond preset rate when the air at the heat supply is above said secondpreset temperature.

It is a second object to provide a fan for such as system which fan atnormal speed in one direction will cause the air in the system to fiowat said first preset rate and at normal speed in the other directionwill cause the air in the system to flow at said second preset rate.

It is a third object to provide such a fan adaptable for use with thereversing motor of the above noted U. S. patent.

It is a fourth object to provide a condition responsive control meansadapted to run said motor operated fan in one direction of rotation atnormal speed on the attainment of one preset value of a condition and torun said motor operated fan in the other direction of rotation at normalspeed on the attainment of a second preset value of said condition.

How these and other objects are attained will be understood from thefollowing description referring to the attached drawing in which- Figure1 is a schematic drawing showing the electrical circuits and devices ofthis invention when the motor is at rest or in an unenergized condition.

Figure 2 is a schematic drawing showing the electrical circuits anddevices of this invention when the motor is operating at normal speed inone direction of rotation.

Figure 3 is a schematic drawing showing the electrical circuits anddevices of this invention when the motor is operating at normal speed inthe other direction of its rotation.

Like numerals of reference denote like parts in the several figures ofthe drawing.

Referring now to the drawing, shown schematically at M is a reversingsingle phase motor of the type shown in the above noted Sprague PatentNo. 2,382,827 but equipped with a reversing starting switch mechanism ofthe type shown in Sprague, et al., Patent No. 2,586,734 issued February19, 1952. As above described for my system and as indicated in Figure 3this motor would be drivably connected to a fan wheel adapted with itscasing 49 to deliver about one-third the amount of air when running atnormal speed in one direction that it would deliver when running atnormal speed in the other direction. The fan casing 40 would be part ofa force warm air heating system furnace installation as previouslyreferred to.

Shown schematically at R is reversing magnetic switch or relay which 1would preferably mount on the motor frame to simplify the wiring of therelay to the motor.

Shown schematically at C is a control instrument which wcuid mount onthe bonnet of the furnace and would replace the usual fan switch theremounted in a forced warm air heating system.

Motor M is shown to have a running winding 11, a starting winding 2, anda pair of starting switches 13 and 14.

Relay R is shown to have two normally closed switches, 15 and 16, twonormally open switches, 17 and 18, and an operating coil 19.

Control instrument C is shown to comprise two condition responsiveswitches 24 and 21, switch 2% having a stationary contact 22 and amovable contact 23 carried on a bimetallic blade operator 24, whileswitch 21 has a stationary contact 25 and a movable contact 26 carriedon a bimetallic blade operator 27. Switch 29 would be set to close at alow air temperature of, say, 110 F., while switch 21 would be set toclose at a higher air temperature of, say, 140 F., although bothsettings would be adjustable and settings would be selected to give bestoperation on a particular job.

It is seen that power line L1 is connected to one side of each of theswitches 29 and 21. Power line L2 is connected to one side of motorrunning winding 11 to one side of operating coil 19, to one side ofnormally closed switch 16, and to one side of normally open swi'ch 17.Contact 25 or" switch 21 is connected to the other side of operatingcoil 19. Contact 22 of switch 26 is connected to the other side of motorrunning winding 11 and to one side each of normally closed switch 15 andnormally open switch 18. Gne end of starting winding 12 is connected tothe other sides of switches 17 and 15. The other end of starting winding12 is connected to both switch blades 23 and 2? of starting switches 13and 14 respectively. Stationary contacts 36 and 31 respectively ofswitches 13 and 1d are connected respectively to the other sides ofswitches 18 and 16.

With this circuit arrangement if the air temperature is beiow thesetting of switch 21), the system is as shown in Figure l with nocircuits complete from L1 to L2.

When the air temperature rises so that switch 20 closes, motor runningwinding 11 is energized from L1, L2 through switch 29, and startingwinding 12 is energized from L1, L2, through switches 20, 14, 15, and16. The motor starts up and before it gets up to normal speed thedirectional centrifugal operator of switches 13 and 14 open switch 14and leaves switch 13 closed. See the above noted patents. The conditionof the system is now as shown in Figure 2, with the motor running in thedirection of low fan output.

As the air temperature continues to rise and finally reaches the settingof switch 21, switch 21 closes and energizes relay operating coil 19from L1, L2. Relay R operates to open normally closed switches 15 and 16and close normally open switches 17 and 18, thus energizing startingwinding 12 from L1, L2 through switches 21 13, 1? and 18. Startingwinding 12 being thus energized in opposite phase to its previousenergization it will have the effect of slowing down the motor to zerospeed and then bringing it up to speed in the opposite direction ofrotation. As the motor stops switch 14 will close and as it starts inthe opposite direction switch 13 will open, thus leaving the motor inthe condition of full speed operation on the running winding only in thedirection of rotation of maximum air delivery by the fan 49. Thiscondition is shown in Figure 3.

It is apparent from the above description and the drawing that the fanwill be stopped when the air temperature is below the setting of switch21 the fan will be running at normal speed in the direction of rotationof reduced air flow when the air temperature is between the settings ofswitches 20 and 21, and the fan will be running at normal speed in thedirection of rotation of maximum air flow when the air temperature isabove the setting of switch 21.

Having thus explained some of the objects of my invention, described theconstruction of one form of my invention and explained its operation, Iclaim:

1. in an air flow control system adapted to supply air at one rat inresponse to the attainment of one value or" a condition and to supplyair at another rate in response to the attainment of another value ofsaid condition, said system comprising a fan adapted at normal speed tosupply air at said one rate in one direction of rotation and at saidother rate in the other direction of rotation, said fan being adapted todeliver air in the same direction irrespective of the direction of itsrotation, a reversible electric motor adapted to drive said fan, asource of electric power, and a condition responsive control meansadapted at one value of said condition to energize said motor from saidpower source to rotate in one direction of rotation and at another valueof said condition to energize said motor from said power source torotate in the other direction of rotation.

2. Means for selectively driving a fan in either direction of itsrotation in selective response to two selected values of a condition,said fan being adapted to deliver air in the same direction irrespectiveof the direction of its rotation, said means comprising a source ofelectric power, a reversible electric motor adapted to drive said fan inthe selected direction of its rotation, a first normally open conditionresponsive switch, a second normally open condition responsive switch,and circuit means adapted on the closure of said first switch toenergize said motor from said power source for one direction of rotationand on the closure of said second switch to energize said motor fromsaid power source for the other direction of rotation.

3. Means for selectively driving a fan in either direction of itsrotation in selective response to two selected values of a condition,said fan being adapted to deliver air in the same direction irrespectiveof the direction of its rotation, said means comprising a source ofelectric power, a reversible electric motor adapted to drive said fan inthe selected direction of its rotation, a first normally open conditionresponsive switch, a second normally open condition responsive switch,and circuit means adapted on the closure of said first switch toenergize said motor from said power source for one direction of rotationand on the additional closure of said second switch to energize saidmotor from said power source for the other direction of rotation.

4. Means for selectively driving a fan in either direction of itsrotation in selective response to two selected values of a condition:said means comprising a source of electric power, a reversible electricmotor adapted to drive said fan, a first normally open conditionresponsive switch, a second normally open condition responsive switch,and a relay means; said motor comprising a running winding, a startingwinding, :1 first starting switch, a second starting switch, resilientmeans biasing said starting switches towards their closed positions andmeans responsive to the direction of rotation of said motor selectivelyto open one or the other of said switches when said motor is operatingin one or the other of its directions of rotation; said relay meanscomprising a first normally closed switch, a second normally closedswitch, a first normally open switch, a second normally open switch,electrical operating means for said four last mentioned switches adaptedwhen energized to open said normally closed switches and close saidnormally open switches; together with circuit means adapted when saidfirst condition responsive switch is closed to energize said runningwinding of said motor from said source of power and to energize saidstarting winding of said motor from said source of power in one phaserelation to said running Winding through said first starting switch,said two normally closed switches and said first condition responsiveswitch, and when both said condition responsive switches are closed toenergize said electrical operating means from said source of power andenergize said starting winding of said motor in an opposite phaserelation to said running winding through said first condition responsiveswitch, said second starting switch and said two normally open switches.

References Cited in the file of this patent UNITED STATES PATENTS

